An organic light-emitting diode (OLED) is called as a third-generation dreamlike display technology as it has the following advantages: active light-emitting, good temperature characteristic, low power consumption, fast response, being flexible, ultra light and thin, and low cost. At present, with the continuous funding, research and development of manufacturers all over the world, an OLED panel display technology is becoming a more and more mature mass production technology, and a market requirement thereof is growing rapidly.
There are mainly two kinds of OLEDs in terms of light-emitting direction, i.e., a bottom-emitting OLED and a top-emitting OLED. The bottom-emitting OLED refers to an OLED where light is emitted from a substrate, and the top-emitting OLED refers to an OLED where light is emitted from a top of a device. The top-emitting OLED may not be influenced whether light can pass through the substrate or not, therefore an aperture ratio of a display panel may be improved effectively, thereby expanding a thin film transistor (TFT) circuit design of the substrate and expanding a scope of electrode materials to be selected, which is beneficial to an integration of the device and the TFT circuit.
Although the OLED may improve device efficiency, narrow a spectrum and improve color purity, the OLED generally is of a strong microcavity effect. Due to the microcavity effect, an electroluminescence spectrum of the OLED may vary with a viewing angle, and an efficiency of the OLED may decrease significantly when the viewing angle is large, i.e., the efficiency of the OLED may depend on the viewing angle due to the microcavity effect, which is an obvious disadvantage for a high-precision panel display.